The present invention relates to clear, single-phase liquid detergents. More specifically, compositions comprising an anionic detersive surfactant in its alkaline earth metal form, a nonionic detersive surfactant and bis(styrylsulfonate)biphenyl as a fabric brightener provide superior detergency performance without undesirable precipitation of the brightener.
Heavy-duty, built laundry detergents have historically been provided in the form of granules. More recently, however, it has been recognized that excellent detergency performance can be secured using unbuilt detergents comprising a mixture of detersive surfactants and materials such as alkanolamines. The advent of such compositions has made it possible to provide heavy-duty laundry detergents in liuqid form.
Liquid compositions offer several advantages over solid compositions. For example, liquid compositions are easier to measure and dispense into a laundering liquor. More importantly, liquid compositions are especially useful for direct application to heavily soiled areas on fabrics, after which the pre-treated fabrics can be placed in an aqueous bath for laundering in the ordinary manner.
Fabric brighteners, or "optical bleaches", are a well-recognized type of laundering adjunct commonly found in granular detergent compositions. Brighteners are especially useful when laundering white fabrics and, when properly selected and used, contribute substantially to the overall appearance of the laundered fabrics.
Various water-soluble stilbene-based brighteners and their method of preparation are disclosed in Canadian Pat. No. 823,683, 9/23/69, incorporated herein by reference. The bis(styrylsulfonate)biphenyl brightener disclosed in Canadian Pat. No. 823,683 is especially useful, inasmuch as it is stable in the presence of hypochlorite bleaches commonly used in laundering liquors. Unfortunately, however, this brightener is precipitated by the relatively high concentrations of alkanolamines commonly used as detergency boosters and pH control agents in concentrated heavy-duty laundry detergents. Accordingly, it has not been possible heretofore to prepare a clear, homogeneous, builder-free heavy-duty liquid detergent containing an effective level of bis(styrylsulfonate)biphenyl.
By the present invention it has been discovered that the alkanolamines used in heavy-duty liquids can be omitted, while retaining excellent cleaning performance, if an anionic detersive surfactant component is used in the composition in its magnesium or calcium form and in the manner disclosed hereinafter. While minor amounts (i.e., less than about 1%) of alkanolamines can optionally be present in the compositions herein to adjust pH, the use of detersive amounts (i.e., about 1%, and greater) of the alkanolamines is avoided, thereby overcoming the brightener precipitation problem. Compositions prepared in the manner of this invention provide heavy-duty detergency performance fully equivalent to that of compositions containing high, detersive amounts of alkanolamines. Moreover, the compositions herein are fully compatible with the desirable bis(styrylsulfonate)biphenyl brightener.
The stable, clear, homogeneous liquid detergent compositions provided herein are characterized by their excellent detergency performance and low cost, which is due in part to the replacement of the relatively expensive alkanolamines with an alkaline earth metal, and in part to the use of the quite efficient bis(styrylsulfonate)biphenyl brightener in place of other types of brighteners.